6 tile offset in "Duck Tales" when using a rope

Hi guys,

I'm trying to figure out another problem, that has been keeping me busy for a few days now.
In "Duck Tales", whenever I use a rope / chain to go up or down, I get a weird 6-tile offset (see attached GIF).

When further investigating, the Y-Scroll value immediately starts at 6 when going down. First, I thought I might be doing something wrong, and that my value is wrong (even though Ice Climber works perfectly), but after a bit more research it turns out, Mesen has the same value(s) [read, the last writes to 2006]:



24c0 -> Y-Scroll 6
24e0 -> Y-Scroll 7
etc.

This can also be seen, when looking at the PPU Viewer in Mesen, the viewport is actually lower than what is visible in the actual window.

These values are achieved through Loopy's scrolling docs, including v, t, x, w.

Can someone point out to me what I'm doing wrong? I already thought it has something to do with the UI (that seems to be 6 tiles high as well), but I can't come up with something logical.

Thank you so much in advance!

The scroll position changes in the middle of the screen. At the bottom of Mesen's PPU viewer there is a "scanline" option. If you set this to 0, it will show you instead the scroll position for the top of the screen where the status bar is.

Makes sense, it's static as the UI is always static. But how can I get rid of this 6 tile offset?

Though, perhaps the problem is that when you split the Y scroll with $2006 you should be setting that position immediately? It is not relative to the top of the screen. If you set the Y scroll to 50 on scanline 70, you will see nametable line 50 on render scanline 70. It is not nametable line 50+70 as if it was relative to the top of the screen. It starts over at that split point.

That's actually exactly the same thing I was thinking about right now. So, I should set the Y-Scroll relative to the scanline it is being set on! I will try that, thanks!

I had to account for negative (relative) scrolling values, but now everything looks as it is supposed to be! Thanks you so much!